Cyfluthrin (EW 050)-impregnated bednets in a malaria control program in Ghassreghand (Baluchistan, Iran)

In a study carried out in the Ghassreghand Division (Baluchistan, Iran) fro m March through November 1995, efficacy of cyfluthrin-impregnated bednets w as compared to that of untreated nets, in relation to malaria control. Ten villages with a total population of 4,572 and 3 villages with a total popul ation of 1,935 Were used as treatment and control, respectively. The collec tion, impregnation (target dosage of 40 mg active ingredient [AI]/m(2)), an d redistribution of the nets (9% nylon, 52% light cotton, 30% medium cotton , and 9% heavy cotton), carried out in mid-April, were done by local health workers, supervised by the senior research staff. Anopheles culicifacies w as considered to be the main vector of malaria in the named area. This spec ies is mainly zoophilic, endophilic, and exophagic. The initial uptake of t he insecticide was lower than the target dosage, with high variation (nylon , 12.5 +/- 5.4 mg AI/m(2); light cotton, 33.3 +/- 26.1 mg AI/m(2); medium c otton, 25.9 +/- 20 mg AL/m(2); heavy cotton, 17.6 +/- 12.5 mg AI/m(2)). The use of impregnated mosquito nets (used primarily outside) had no significa nt effect on the incidence of malaria. No difference was detected in the pa rasite density of patients with positive slides. No significant effect was observed in the parous rate, human blood index, and sporozoite rate of anop heline vectors. Only the indoor resting densities of An. culicifacies and o ther malaria vectors were drastically reduced after the introduction of the cyfluthrin-impregnated nets into the treatment villages. The residual acti vity of cyfluthrin was lower than expected. The mortality of anophelines br ought in contact with the treated nets for 3 min in bioassays dropped to le ss than 55% in 3 months. The loss of chemical activity was greatest for the light cotton nets, followed by the medium cotton nets. Cyfluthrin-treated nets were mildly irritating to host-seeking female anophelines in the labor atory. The protective rate of impregnation (all fabric kinds included) in p reventing female mosquitoes from biting through the impregnated nets was in itially 5-6 times that of the nonimpregnated nets. The study did not detect any significant difference between the use of untreated versus impregnated bednets in the Ghassreghand area. In planning future medium-scale trials, comparison of new compounds and formulations to the more widely used pyreth roids such as permethrin and deltamethrin is highly recommended.